Short wave signaling



Sept L i935 N. E. LINDENBLAD SHORT WAVE SIGNALING Filed April 5, 1932 7 ShetS-Sheet 1 Q y W..

Sept. l, 1936-.

N. E. LINDENBLAD SHORT WAVE SIGNALING 7 Sheets-Sheet 2 Filed April 5, 19:52

Sept. 1, 1936- N. E. I {NDENBLAD SHORT WAVE SIGNALING Filed April 5, 1932 7 Sheets-Sheet 3 INVENTOR N\L.5 E. LINDENBLAD BY 7# Q g f l /wU-Ol/ ATTORNEY SHORT WAVE S IGNALING Filed April 5, 1932 7 Sheets-Sheet 4 @ggf INVENTOF?. NILS E LINDENBLAD B" 7%. @WV

ATTORNEY Sept. l, 1936.

N. E. LINDENBLAD SHORT WAVE SIGNALING Filed April 5, 1932 '7 Sheets-Sheet 5 ATTORNEY Sept- 1, 1936- N. E. LINDENBLAD SHORT WAVE SIGNALING Filed April 5, 1932 7 Sheets-Sheet 6 INVENTOR NlLS E. LINDENBLAD ATTORNEY Septn l, 1936. N. E. LINDENBLAD 2,052,576

SHORT WAVE SIGNALING l Filed April 5, 1932 7 Sheets-Sheet '7 -"lip wmf/q Alm/HEP /iaz k [-Hw 6fm/sm INVENToR ost/m70? ffm NlLs E. UNDE LAD ATTORNEY Patented Sept. l, 1936 PATENT OFFICE SHORT WAVE SIGNALING Nils E. Lindenblad, Port Jefferson, N. Y., assignor to Radio Corporation of America. a corporation of Delaware Application April 5, 1932, Serial No. 603,310

This invention relates to the short wave signaling art and appertains especially to the frequency control, generation, frequency multiplication, modulation and electromagnetic propagation .of ultra short waves, particularly in the rame of wavelengths below two meters and of the order of frequencies above one hundred fifty million (150,000,000) cycles per second.

Pushpull oscillation generators of the regenerative vacuum tube type have been used for the generation of rather high frequency waves. However, the ordinary pushpull system as now known will prove impractical and in fact, inoperative in the ultra short wave length eld approaching the high frequencies, with which I am now dealing. This failure is due to the large interelement capacity of the electrode elements of the tubes which prevents the building up of the necessary high frequency controlling voltages for oscillation production. However, as pushpull arranged oscillators present many advantages due l to their electrical and mechanical symmetry, it is an object of my present invention to improve their construction and operation whereby they may be utilized to produce oscillations at desired very high frequencies which in turn are frequency multiplied, according .to another feature of my invention, to be more fully referred to and described hereinafter, to ultra short waves at high power and of frequencies of the order of magnitude of 450,000,000 cycles per second.

To make the oscillator operable for my purposes I tune not only the control grid and plate circuits, by means of circuits having substantially uniformly distributed inductance and capacity, but I also tune the cathode energizing circuits.

In this manner the impedance formed by the various tube electrodes and their associated circuits are more easily compromised to give high alternating potential variations at more nearly correct inter-electrode phase, resulting in such an optimum relationship between these factors, which produces a maximum of output and dependability of performance.

As'I propose, as I shall describe more fully hereinafter, to frequency multiply the primary ultrashort waves so generated it is evident that even a relatively small shift in frequency of the primary or master oscillating system will result in a large Ashift in frequency of the frequency multiplied output, covering an extremely wide band of frequencies. Such action, of course, would render the system practically useless for superheterodyne or super-regenerative reception, for it is (Cl. Z-36) quite impossible to build a receiver with a sufciently wide band pass to accommodate the shift in frequency which would ensue from the frequency multiplication of the primary controlling oscillations should the primary oscillations vary 8 over what would normally be a small range. Accordingly, a further object of my present invention is to provide some means for making especially constant the frequency of the primary master oscillation generator. To do so, I make use 10 of, in my improved oscillator, preferably, long line frequency control systems such as described by C. W. Hansell in his U. S. Patent, No. 1,945,546, granted February 6, 1934.

In view of the large control which the tuned 15 cathode or lament circuit of my improved oscillator has upon the frequency of oscillations generated, I prefer to couple the long resonant transmission line for frequency control to the tuned filament circuit. The line acts, as described 20 in the patent referred to, in one sense as a phase shifter, waves traveling down the line being fed Vbaci: a time later proportional to the number of waves contained in the line. Hence, with a shift in frequency there is a shift in phase between 25 the incoming and reflected wave proportional to the `number of wave lengths on the line, and this shift in phase is in such a direction as to pull the frequency of oscillations generated back into step with the frequency for which the line is the correct number of half wavelengths long. Or, more simply, the line laction may be described as that of a ywheel which does not permit anything connected thereto to run ahead or lag behind.

Although these resonant lines are made of the correct length for al desired operating frequency, yet, I have found that the frequency control, when using a. long line for that purpose, tends to shift or jump to frequencies corresponding to the addition or subtraction of one or possibly more half waves to the length of the line. This is especially so if the line is very long, as it is preferably made, relative to the wave length used. Since it does not require a very large frequency jump to cause this frequency jumping phenomenon, a further object of my present invention is to improve the frequency stabilizing effect of such long line frequency control systems and to prevent these undesirable frequency jumpovers. 'Io eliminate this frequency shift condition I have found that the most simple expedient is to place impedances across voltage Anodal points on the long transmission line, the impedances preferably being of a value equal to the surge oscillating. Consequently, the circuit does not choose, so to speak, this mode of operation.

If it is desired to prevent even multiple half wave length jumps, an additional resistance or impedance should be located at another voltage nodal point at the correct operating frequency, approximately one-quarter wave length away from either end of the line.

It should be clear, however, that the positions of these impedances are not limited to the positions specifically mentioned, but may be placed, for example, all along voltage nodal points on the long line frequency controlling means. Also, it is not necessary that the impedances be made equal to the surge impedance of the line, but may vary in value and may be either inductors, condensers, resistors, or any combination thereof `taken any number at a time.

As an alternative method of controlling the frequency of my primary oscillation generator, I may adjust the voltages and constants of the master oscillator circuitl such that it is just on the verge of oscillating, although the master oscillator may be used as an ordinary amplier and not adjusted near its oscillating value. Then, by using a low powered oscillator such as acrystal controlled oscillator, or a higher powered oscillator such as a long line frequency controlled oscillator of a desired wave length, whose outputs preferably are frequency multiplied either in known fashion or preferably by the frequency multiplication means to be described hereinafter, the primary oscillator is brought into oscillation and is frequency stabilized by the applied output of the frequency controlling .or frequency multiplied oscillations from one of the sources mentioned. In this manner, after the 4frequency multiplied energy is brought to the same frequency as that which it is desired to produce in the power oscillatorrand applied thereto `the primary or master oscillation generator is set into operation by the guiding or frequency multiplied oscillations. A lesser frequency controlling action may be obtained by allowing the primary oscillator to oscillate while feeding controlling oscillations thereto. The latter of which, in that case, pull or lock the master oscillator into step with the constant frequency guiding oscillations which as indicated may be the frequency multiplied output of, say, a crystal controlled oscillator. However, as indicated, it is preferable that the primary oscillator be just on the verge of oscillating and be set into oscillation by the supplied low power constant frequency oscillations.

An additional source of variation in frequency of the master or power oscillator resides in variations in potential supplied to, for example,y the plates or anodes of the same. Accordingly, a further object of my present invention is to remedy this defect and to do so, I provide, as will be explained more fullyhereinbelow, a vacuum tube voltage regulator which maintains substantially constant voltage on the anodes of my master oscillator and if desired on other tubes and/or other electrodes of my improved short wave system,

despite variations in voltage of the energy source.

So far I have been dealing with, in the main, frequency control of the master oscillator. I repeat, also, that with the system and frequencies as so far described, a much higher power output of the master oscillator will be obtained relative l to the power obtainable, 'for example by using known high frequency oscillators such as those of the Barkhausen-Kurz type. However, it is a further object of my present invention to provide a system for obtaining still higher constant frequencies of, for example, 450 thousand kilocycles per second, at higher power as compared to any system heretofore known.

To obtain the higher frequencies, I frequency multiply the oscillations from the master oscillator. However, ordinary frequency multiplication will, to say the least, fail to give a satisfactory working power output. Accordingly, it is a further object of my present invention to provide a frequency multiplication method and system which will give high power output at these ultra short frequencies. To do so, I use one or more electron discharge devices so adjusted that only relatively small fractions of the positive half cycles of input energy produce flow of electrons. Moreover, to insure operation at the frequencies involved as well as to increase efliciency and output, I tune, preferably by the use of circuits having substantially uniformly distributed inductance and capacity, the cathode or filament heating circuit of the frequency multiplier as well as the anode and controlling grid circuits.

The main feature, however, which I utilize to increase the power output of my frequency multiplier, is the application of a magnetic field to the electron discharge device or devices forming the frequency multiplier. The application of this magnetic eld I have found, substantially augments the output of the frequency multiplier. The effect of this magnetic field may be explained by stating that it produces a tangential approach of the electrons, within the tube, close to the output electrodes and thus results in a sharper stopping and starting of the electron flow than if the electrons approached radially. As the positive peak grows stronger it will break these tangentially moving electrons away from their orbits, as the distance from the orbits to the output electro-de is small, quicker and larger electronic action can be obtained.

In addition, it will be found, at the frequencies under consideration, that ordinary methods of modulation such as varying grid voltage or plate voltage applied to the master oscillator would introduce undesired frequency variation or modulation in the output of the oscillator. To attempt, also, to apply such schemes to the frequency multiplier described hereinabove,would result in similar output variations because of the reaction of the multiplier on the master oscillator. This frequency varying effect is not altogether eradicated, I have found, by the insertion of a buffer amplifier between the master oscillator and frequency multiplier although buer amplifiers have proven apt solutions in lower frequency fields. Moreover, I have also discovered that conventional absorption schemes for modulation fail and in general are inoperable at the high frequencies here involved.

A further object of my present invention is, therefore, to provide a modulation system for these extremely short wave length ,oscillations of electrical energy which will give substantially 75 pure amplitude modulation and be substantially free of undesired frequency modulation. To do so I use a modulator somewhat similar to my improved frequency multiplier in that .it makes use of one or more electron discharge devices to which is applied a magnetic field. As before, the control grid, anode and cathode heating circuits are tuned. However. if desired, the anodes may be left floating that is, disconnected from circuit entireiy, the grids or control electrodes, preferablyv those close to the filaments or cathodes being connected to a voltage maximum point in an output circuit of the frequency multiplier as will be described more in detail hereinafter, whereby the output is varied in amplitude in accordance with the modulation applied to the modulator.

In my United States Patents Nos. 1,884,006 and 1,927,522, granted October 25, 1932 and September 19, 1933, respectively, and in United States Patent No. 1,974,387, granted to P. S. Carter September 18, 1934, there have been disclosed antenna systems which make use of linear conductors long relative to the operating wave lengths and which in general are highly satisfactory for short waves. However, I have discovered that, at the frequencies with which I am now dealing, corrosion of the wires, moisture thereon, and sagging thereof, have a decidedly deleterious effect on the propagation of these waves. Accordingly, a further object of my present invention is to provide a radiating system suitable for the ultra short waves generated and frequency multiplied according to my present invention. In general this system comprises a plane, smooth, metallic reflector having suitably spaced therefrom a plurality of linear radiators. This system will be described more fully hereinafter as will many other objects, features and advantages of my present invention. Further description is given' by aid of the accompanying drawings, wherein:

Figure l shows a preferred embodiment of my ultrashort wave length transmitting system utilizing among other things my improved master oscillator and my improved magnetic frequency multiplier and modulator.

Figure 2 illustrates a system wherein frequency control of the master oscillator is accomplished by means of a frequency guiding arrangement,

Figure 3 illustrates an alternative antenna arrangement which may be used with either of the systems shown in Figure 1 or 2,

Figure 4 illustrates a modified modulating arrangement,

Figure 5 is a wiring diagram given by way of explanation of my present invention,

Figure 6 illustrates a single tube rather than a pushpull tube transmitting arrangement utilizing many features of my present invention,

Figure 7 is a detail of apparatus used in Figure 6,

Figure 8 illustrates an alternative antenna coupling circuit for use in connection with the arrangement shown in Figure 6, and,

Figure 9 illustrates another form of my invention utilizing my improved frequency multiplication features and phase modulation.

Before giving a detailed description -of the various elements forming part of my system, I shall briefly outline the corelationship and the operation of the various elements comprising a. preferred form of my invention which is illustrated in Figure l (see-Sheets 1 and 2).

Very high frequency oscillations generated vvby my improved master oscillator M. `0. are fed through the inductive coupling arrangement C to a buffer amplifier B. A. This buffer amplier tends to prevent reaction of the magnetic frequency multiplier M. F. M. upon the master oscillator. Coupling between the buffer amplifier and the magnetic frequency multiplier is established through a similar coupling arrangement C-I. The magnetic frequency multiplier frequency multiplies energy from the master oscillatorbuffer amplifier arrangement, and feeds the frequency multiplied energy into an absorption circuit A. S. From the absorption circuit the energy so frequency multiplied, is fed through another coupling scheme C-2 by way of transmission line arrangement T. L. to a transmitting antenna system T. A., having a unidirectional radiant characteristic.

As conventional methods of modulation either prove ineffective, or introduce, as already pointed out, undesired frequency modulation effects, I have provided an improved modulator M. M. or what I term a magnetic modulator, coupled to the absorption circuit A. S. This magnetic modulator is actuated in turn by the incoming modulation amplified by audio amplier A. A. I have found further, that with the high frequencies involved herein, ordinary absorption methods will not do for modulation purposes, as they prove ineffectual. But with my improved modulator, not only is modulation effected for complex waves such as voice signals, but, there is a material absence of reaction back upon the master oscillator, as a result of which the Waves radiated are substantially and purely amplitude modulated. 'I'his is because with my improved modulator I can modulate the frequency multiplied energy directly and alone. The frequency multiplied energy is only a portion of the total power from the master oscillator and, therefore, the reaction is proportionally smaller.

Frequency variation in the transmittedwave is further reduced by maintaining the voltages applied to various electrodes of my system con'- stant despite fluctuations in the D. C. voltage from the D. C. voltage or potential source, by means of my improved vacuum tube voltage regulator system V. R.

Referring to the master oscillator of my improved system, it will be seen that it comprises a pair of electron discharge devices 2, 4, having a tuned grid or control electrode circuit 6 and a tuned anode or plate circuit 8. The tuned grid circuit 6 for the grid electrodes or electrodes III, I2 adjacent the cathodes I li, I6 of electron discharge devices 2, li, comprises a pair of parallel conductors I8, 20 having substantially uniformly distributed inductance and capacity and arranged relatively close together so that radiation therefrom will be practically nil. The tuned circuit 6 is terminated by short circuiting strip or conductor 22 grounded through a resistor 24 which may be made variable if desired. Due to grid rectification, by a suitable choice of value for resistor 24, the control electrodes II), I2 may be maintained at a suitable operating potential, but it is to be clearly understood that these grids may be polarized by substituting for resistance 24 a suitable source of unidirectional electromotive force such as a battery and potentiometer.

The tuned anode circuit 8 is formed like the tuned grid circuit. That is, the tuned circuit 8 is formed of a pair of relatively closely spaced conductors 26, 28, having substantially uniformly distributed capacity and inductance. While the grid circuit 6 has been shown tunable by movement of slide 22 along conductorsl I8, 20, the anode circuit is shown tunable by means of conductive trombone slide arrangem'ents'ill, 32. The

sliding members and the stationary members of the trombone arrangements are arranged so as to be in conductive relationship `with respect to each other so that the potential supplied through Conductor 34. which, by the action of the voltage regulator is constant despite variations in voltage from the plate voltage rectifier 36, may reach the plates or anodes 38, 40 of the electron discharge devices 2, 4.

The cathode heating circuit may be traced from the grounded conductor 42, connected to the D. C. filament source 44, through short circuiting or conducting strip 46, through conductors 48, 50 insulatingly supported within conducting4 tubes 52, 54 through the outer legs of the hiaments I4, I6 and back through the inner legs of the filaments over the conducting tubes; 52, 54 through current varying or voltage controlling resistor 56, to the other conductor 58 of the D. C. lament bus. The return to the conductor 58 is accomplished through the conducting or short circuiting strap 60., which is made movable along tubes 52, 54 so as to enable tuning of the filament or cathode energizing or heating circuit which is an important feature in my improved master oscillator.

Because of the close contiguity of the conductors 48, 52, they act as a single conductor for the high frequencies involved. However, to insure such action throughout the entire length of the lament or cathode heating circuit, by-passing condensers 62, 64 are provided for the conductor system 48, 52 and 50, 54 respectively.

It is to be noted also, that variable connections 66, 68 areprovided for the long line for frequency control comprising preferably a pair of closely spaced linear conductors 10, 12 short circuited at their far ends by short circuiting conductive strap 14 movable along the conductors 10, 12.

In order to have the master oscillator operate at the exceedingly high frequencies contemplated, to provide basic master oscillations of fundamental frequency, it is essential that the cathode energizing circuit be tuned as described. Otherwise, due to the 10W capacity reactance between the elements within the tube on one hand, and too great electronic time lag on the other hand, sufficiently optimum controlling potentials will not be set up on either the anodes or control grids, and this of course would not provide variation in the electron streams within the tubes at these high frequencies and therefore the desired high frequency output would not be produced. However, by tuning the various circuits as described, and by making the cathode ends of the tuned filament circuit of correct impedance, by adjustment of slider 60, it will be found that the vcircuit will gp into oscillation and produce an appreciable high output at frequenciesA heretofore diicult to attain with the ordinary push-pullv circuits.

It should be obvious, therefore, that the cathodes have a substantial control on the frequency of oscillations generated and accordingly, I have connected the long line 'frequency control system comprising the conductors 10, 12 -to the tuned cathodeenergizing circuit. The line when short circuited by strap 14 is tapped to the tubes or hollow cylinders 52, 54, which, because of their large diameter and relativelylow reactance, carry high frequency energy, the inner conductors serving in general to form a path for the unidirectional or low frequency heating current. Incidentally, it may be pointed out that throughout my improved system, to enhance frequency stability, uni-directional heating currents are employed; although alternating heating currents utilizing heater type of tubes may be utilized although as a result thereof there may be some sacrifice in frequency stability.

The action of the long resonant line, so termed because it is many wave lengths long relative to the operating or controlled wa-ve length, is more fully described in United States Patent No. 1,945,546, supra. Briey, frequency stabilizing action of the line may be ascribed to the fact that waves travel down the line and return by reflection to the input end of the line. Now, should there be a shift in frequency such that a half-wave length ingoing wave is not contained in the line a whole number of times, then it is reflected back from the far end of the line to the input end of the line with a phase shift augmented or multiplied by the number of half waves contained in the line. This phase shift, it will be found, is in such a direction as to pull the oscillator back into step in frequency with the frequency for which the line was made a corresponding whole number of half wave lengths long and, because of the augmented phase shift produced by the choice of long length for the line, the oscillator is rapidly pulled back to a correct operating frequency. This rapid return adjustment is still further increased by virtue of the fact that the line or frequency stabilizing or controlling means, is coupled to the tuned cathode circuit, which, as already pointed out, is very effective in controlling the generation of oscillations by the push-pull arranged electron discharge devices 2, 4. In addition, coupling to the lament circuit is preferred as it is more stable.

The line may be left open circuited, in'which case strap 14 would be omitted and the line cut to the correct length. However it is preferred to terminate the line, for structural reasons, by a short circuting strap so that the terminated end is at a voltage nodal point.

In practice the line has shown itself to be a simple and effective frequency controlling means. However, there is a tendency for frequency shifts corresponding to the addition or subtraction of possibly one or more half waves. This should be evident inasmuch as the line would be exactly divisible by such correspondingly spaced freuencies about .the desired frequency of opera- To prevent such frequency jump-over or shift, I connect across voltage nodal points on `the long line conductors 10, 12, resistors 16, 18, which, in Fig. 1 have been illustrated as being placed onequarter and one-half thev length of the line rev spectively, away from the voltage ,maximum end or left-hand end of the line. It will be found that the resistor, which may be made equal in value to the surge impedance of the line, placed approximately at the center thereof, will prevent odd multiple half wave jumps in frequency. Similarly, a resistor placed one-quarter away from either end of the line will prevent jumps in frequency corresponding to even multiples of a half wave length of the desired operating frequency. Should it bedesired to prevent even ones alone, the resistance at the mid-point is no` longer necessary and may be removed, and, should it be desired to prevent odd half wave jumps alone, the

resistor at the quarter ends may be disconnected. Moreover, if desired, these resistors, or other impedances, for example, condensers or inductors, or combinations thereof, may be placed across the line at any number of voltage nodal points thereon. It is to be noted however that by special choice of impedances it may not benecessary to locate these impedances at the nodal points.

The action of these resistors or impedances to prevent the frequency jumps or shifts may be explained by stating that at frequencies other than the desired frequency, standing waves cannot be set up upon the line because of the heavy` resistiveV loads presented by the4 resistors. In other words, due to the heavy load on the circuit. at undesired frequencies, the building up of voltage maximum points is prevented.

The action of the impedances at the nodal points can also be explained as follows:

The shorter a long line is the broader is the detuning necessary for jumping a certain multiple of half waves. On the other hand, a short line has, for the same reason, less ilne control 'of the frequency. The scheme involved, therel'fore combines the virtues of a long and a short line.

From what has gone on before, it is clear that the placing of these resistors on the line is not limited to the points specically referred to, but

resistors may be placed across voltage nodal points all along the entire length of the long line used for frequency control.

It is, of course, obvious that the line may be connected to the master oscillator in a more conventional way, for instance to the grid circuit or to any other portion of the circuit which may be found expedient. The reason for particularly pointing out the connection to the cathode circuit is that it has proved especially convenient and stable.

Despite the long line for frequency control, slight variations in frequency may be due to variations in plate voltage from plate voltage rectifier 36. To eliminate this source of disturbance I have provided a voltage regulator V. R. which in general may be used in any situation wherein it is desired to obtain a constant voltage from a fluctuating uni-directional source.

'Ihe voltage regulator for the plate supply for electron discharge devices 2, 4 comprises an electron discharge device 80 having an anode 82, a cathode 84, and a control electrode or grid 86. The cathode is energized from a D. C. lament source 88, the voltage applied to the cathode being controlled by variable resistor 90 in series with the cathode filament.

The plate voltage fromsource 36 is fed through a conductor 92 which in turn is connected to ground 94 through resistor 96 and source of potential 98 which may be a D. C. generator or any other suitable source. The source 98 need not be of high current capacity but simply a source applied in reversed polarity relative to the polarity from conductor 92, in order to obtain the proper negative bias on the grid 86. Between conductor 34 supplying potentials to the anodes of the master oscillator tubes, and resistor 96, there is connected another resistor |00. To the point on this resistor connected to conductor 34, there is also connected the anode of electron discharge device 80. The grid 86 of electron discharge device 80 of the voltage regulator V. R.-| is connected to some intermediate point on resistor 96, this point being so chosen that constant Voltage is fed to the master oscillator anodes despite variations in the primary source 36. o

The action of the voltage regulator V. R.-| may be explained somewhat as follows. Adjustments are made so that with acertain current flowing through resistance |00 and resistance 96, the correct potential is applied to the master oscillator anodes. Then, should the plate voltage rectifier source 36 increase in voltage, the voltage of the grid 06 on the voltage regulator tube'80 is increased in a positive direction so that increased current is drawn through resistor |00. Consequently, there is an additional-voltage drop across .the resistor |00 which compensates the added voltage from the plate rectier, as a result of which constant voltage is maintained upon the anodes of the master oscillator tubes.

It should be borne in mind that by this arrangement, nearly complete balancing out of potential variations from source 36 is accomplished as long as the characteristics of the circuit elements remain linear.

Those remarks given in explanation of voltage regulator V. R.| apply with equal force to the voltage'regulator V. R.-2 supplying substantially constant potential from source 36 through conductor |04 to the anodes of the buffer amplifier tubes |06. |08. Hence, a detailed description of the voltage regulator V. R.-2 will not be givenv here as it is felt that its mode of construction and method of operation should be clear from the discussion giv'en of the operation and description of the voltage regulator system V. R.-|.

As already pointed out, constant frequency energy of the order of frequencies heretofore very diilicult to obtain with ordinary regeneratively coupled electron discharge devices, is fed through the coupling arrangement C to the buier amplier B. A. The inductive couplingv C is formed by the single loops ||0, ||2 adjacent each other. and made relatively movable so as to enable variation in coupling, the loop ||0 being included in the tuned transmission line ||4 similar in construction to the tuned anode circuit of the master oscillator tubes. The loop ||2 is part of the tuned anode circuit 8 of the master oscillator tubes 2, 4.

In general, the mechanical and electrical construction of the buffer amplifier and its associated circuits are similar to the circuits of the master oscillator. The energy fed through the coupling C and impressed upon the tuned lament or cathode circuit |20 of the buffer amplifier tubes |06, |08 is reproduced and fed in amplied form through the coupling C| to the magnetic frequency multiplier M. F. M.

By virtue of the trombone slides in the transmission line ||4, coupling the master oscillator through coupling C to the tuned filament circuit of the buier amplifier, the line H4 is made of such a length that it is tuned to the fundamental frequency and that its output ends |22, |24 are suitably matched by the impedance of the filament circuit. The tuning of the filament circuit by adjustment of short circuiting strap or conductor |26 should be such that the cathode ends of the circuit are of optimum phase and voltage to produce optimum performance of tubes |06 and |08.

Although the buffer amplifier may be set' into oscillation by the application of the control potentials from the master oscillator, the buiier amplifier is, by virtue of its tuning, and also by virtue of the application of the frequency controlling currents or potentials from the master oscillator,

guided, forced or locked into step for the production of amplified oscillations, corresponding identically in frequency with those oscillations generated by the master oscillator. This princple is used in the system which will be described in connection with Figure 2,- for controlling the frequency of a master oscillator rather than by use of long lino frequency controlling means illustrated in Figure 1.

It is to be noted that the buer amplifier, if the grid circuit is given a tuning equivalent to grounded grids, is extremely stable. Moreover, although the feedback for such tuning is degenerative, the eihciency is not out to the extent, compared with conventional, balanced or regenerative circuits, that it would at longer waves. The virtue of the arrangement is .that it often solves the problem of circuit stability at very high frequencies. When perfect grounded grid effect is desired, the slider on the grid tuning leads is placed a multiple (first multiple preferably) of a half wave from the grids proper. This then gives the same effect as if the grids were directly shorted together. Due to the dimensions of the glass envelope of a tube, a sufciently direct short at these very high frequencies cannot be accomplished, thus the procedure explained above. It is clear that in actual practice conditions suoh as described are often compromised `with other circumstancesV to give a balanced optimum of performance.

Through the coupling C-i (Figure 1) similar in action and construction to coupling arrangement C, energy of fundamental frequency is fed through variable transmission line |28 formed of conductors |32, |35 of variable length to the anode circuit or input circuit of the magnetic frequency multiplier M. F. M., which anode circuit is composed of conductors |36, |38 directly connected to the anodes i610, |52 of my magnetic frequency multiplier M. F. M. Within the electron discharge devices or vacuum tubes Hifi, |65 of my frequency multiplier there are also the control grids or electrodes M8, |50 adjacent the cathodes or filaments |52, ld respectively. Condensers |53, |55 correspond with condensers 52, @d of the master oscillator and similarly have been illustrated in shunt with the filaments of the magnetic frequency multiplier.

' To prevent the harmonics generated by the frequency multiplier from reacting (or losing energy) backwards upon the buffer amplier and in turn upon the master oscillator, the conductors |32, |36 are tied on to voltage nodal points or current maximum points or low impedance points for harmonic Waves on the tuned anode circuit constituted by conductors |35, |38 of the frequency multiplier. With respect to the fundamental waves, the anode ends of the anode circuit are high voltage or high impedance points. 'Ihese conductors are short circuited by strap |55 which in turn is grounded through conductor |58. A source of potential, may, if desired, be placed in the conductor |58 to maintain the anodes at a suitable D. C. operating potential. However, I have found in many cases, for frequency multiplication at these extremely high frequencies, namely, for example, of the order of magnitude of 150 million cycles per second, or generally, over 100,- 000 k. c. per second, supplied from the master oscillator, that the anodes |50, |42 can be grounded as illustrated.

The output circuit of the frequency multiplier is formed of conductors |60, |62 adjustable in length and tunedto a harmonic, for example, the third harmonic, or in other words, tuned for frequencies of 450,000 kllocycles per second, assuming of course that the master oscillator is adjusted to operate at 150,000 kilocycles per second.

tubular conductors I 68, |10. Filament heatingcurrent may be traced from conductor 58 through voltage regulating resistance |12 through tuning conductor or strap |15 through the filaments |52,

|58 and back through the internal conductors- |64, |66 conducting strap or short circuiting element |16 through conductor |18 to the other side or conductor 42 of the filament heating circuit bus supplied with energy from source M.

By adjustment of strap |74 the cathode circuit is tuned for best matching with the rest of the circuits. 'I'his means it has a compromise optimum for both fundamental and harmonic frequency. The grid circuit' being set for optimum impedance to harmonic energy, this energy readily feeds into and flows through the same and builds up to a. large value.

Now, the frequency multipler as so far described, namely, without the magnetic apparatus illustrated, will not deliver an appreciable output. To increase the output, I apply a uni-directional magnetic field to the electron stream within the tubes |48, |50, in a direction perpendicular to their normal paths of travel from filament to anode. The magnetic apparatus consists of a pair of solenoids |80, |82 through which runs a. yoke |86, preferably of iron of high permeability which may or may not be laminated. The solenoids |80, |82 are serially connected as shown, and supplied through conductors iil, |85 with energizing currents from source `t4 adjustable in value by means -of resistor |88.

It is to be noted that the grids or electrodes itt, |50 adjacent the cathodes |52, |54 are connected to the output circuit formed of conductors |60, |62, within which looped conductor |90 is slidably and conductively arranged for tuning purposes as well as to allow the direct current voltage, generated by grid rectification, across grounding resistor or biasing resistor |92 to manifest itself upon the'control grids .or electrodes.

I'he resistor ft2 is preferably so chosen that the positive peaks of input potential applied to the anodes |50, |52 cause spurts of electrons to impinge upon the control grids or grids adjacent the cathodes. Under such circumstances, without the application of the magnetic field, the harmonic output, if any, will be very feeble. However, by the application of the longitudinally or axially applied uni-directional magnetic field, the output, atharmonic frequencies in the tuned output circuit |50, |52, |90 is materially augmented and of a substantial value.

A qualitative explanation, as well as a possible explanation of this phenomenon is that the electrons emanating from the filaments are curved in their paths and retained by the magnetic field in large quantities in suspension in the space about the cathodes and closely adjacent the control grids. Hence, when the intensity of a positive peak of applied input potential has grown to suflicient strength to bring the electrons to the grids in spite of the curving, the number of electrons which splash against the control grids is considerably larger than that number without the suspension effect. In addition.' it is to be pointed out that this improved action may also be due to the fact that due to the suspending of the electrons within the space closely adjacent the control grids, there is less time diiference between the electrons which travel from the space suspension to the control grids when arrayed on curves almost tangential with the grid relative to the time diierence between radially arrayed electrons. These arrays lare considered in the sense of the motion of the electrons and not in the sense of their actual location. At the high frequencies involved, this time lag effect is, as will be evident, very important, for, unless the electrons impinge upon the output electrodes in unison, the abruptness of variation required to produce a harmonic will never be obtained. This is perhaps better understood if it is pointed out that, the higher the frequency, the more so do the electrons which at a certain moment are confined in the space, represent the total number of electrons taking part in an oscillatory cycle. In other words, due to the extremely short time duration of a cycle relative to the electron velocity it is very important to have the motions of the electrons well disciplined so that their action in unison will overcome the handicap due to the absence of mass action which is readily obtained at lower frequencies.

Thus, the application of the uni-directional magnetic eld causes a sharper impingement of electrons as Well as cut oi of electron flow to the output electrodes upon the start and cessation of the positive peaks of input controlling potentials and it is this sharp starting and stopping of electron flow which is responsible to a large degree for harmonic waves.

In general also, improvement in output as well as in many cases, change from non-operation to operation, or, in otherl words, increased efdciency is obtained by the tuning of such circuits as the filament heating circuits.

In actual construction, I have used with good success electron discharge devices with T-shaped glass envelopes, the longitudinal axes of the anodes of which are substantially parallel to the longitudinal axes of the solenoids l80, |82. Portions of the tube also have been made to extend through openings or orilces drilled into or through themagnetic` yokes, so that the field intensity applied is increased, and so that leakage flux is materially reduced.

It is also to be pointed out in connection with my improved frequency multiplier that the grids or electrodes adjacent the cathodes, have been chosen as output electrodes rather than the anodes. With respect to the fundamental input, because the capacity coupling between the electrodes, that is, between grids and plates, is so great it is immaterial Whether the fundamental input is applied to the grids or the plates.

To more fully appreciate many of the foregoing features of my present invention, it may be well to restate at a slightly diierent angle, some of the problems encountered in producing extremely high frequency energy and the methods which I have employed to overcome them. It should be remembered that some of the outstanding difficulties to be dealt with in producing the very high frequencies, contemplated by the present invention, are the relative slowness of the motion or low velocity of electrons within vacuum tubes at reasonable voltage values, and, the low capacitive reactance of the tube elements at these extremely high frequencies. The vlow velocity of the electrons makes it exceedingly difllcult to time a suilicient number of them for correct illament-grid-plate phase phenomena and the low capacitive reactance tends to limit the voltage swing of the electrodes. The latter, of course, gives only a very small impetus, relative to that desired, to the electrons.

Because of the small distances traversed by the electrons in exceedingly short periods of time under consideration at the extremely high frequencies involved, I have found it advisable to choose the grid, which is nearest the filament, as the frequency multiplier output` electrode. In addition, the application of the magnetic eld at right angles to the normal paths of the electrons is benecial since, in tubes or electron discharge devices with cylindrical elements, the field would cause the electrons to curve in their paths oi travel making the actual electron velocity greater due to this additional eld. Consequently, as the positive swing of the grids increases upon the application of fundamental frequency energy, the electrons actually have a greater velocity than without magnetic field; thus the performance of the electrons is speeded up and they so to speak, break away from their orbits and bridge the short distance to the grid or grids in a shorter time, therebycausing a maximum abruptness in the ow of electrons to the grid and causing a maxlmum amount of harmonic oscillation generation. Moreover, due to the orbital line-up of the electrons by virtue of the uni-directional magnetic field a greater number of electrons may be held in readiness in the space between the lament and grid for the crucial moment when the grid swings suiliciently positive, as a result of which increased output at harmonic frequencies follows.

Further, it may be well to describe the peculiar eifect taking place when a tube is used as a multiplier. The temperature of the filament suddenly rises when the conditions for multiplication are obtained. This is due to bombardment from returning electrons that did not reach the grid. Under static field conditions, the velocity of the returning electrons should be ,zero when they reach the filament, save for the added velocity from thermal influences when they left the illament at the beginning of their `tourney. This thermal velocity, however, only represents a very few volts and could not be responsible for the violent bombardment which the filament is subjected to. The reason for this phenomena is apparently as follows. No electrons leave the filament or the space charge surrounding the same until the grid goes positive. Some time before this, while the grid is becoming less and less negative, the space charge around the lament may swelP out and as this swelling out represents a motion of electrons, these will perform a slow spiral (the spiral due to the magnetic field) towards the grid; and, if there is time enough and the tube dimensions so permit, a few electrons may, if time permits, actually reach the grid before it has changedfrom negative to zero, due to aforementioned initial temperature velocity of the electrons. The bulk of the electrons will, however, not pass to the grid until it goes positive.

The dynamic curve of the grid voltage while it is positive is represented by the top portion of a sinus curve. This portion has the least slopeso while its slope is sufficient to cause the abruptness in the electron iiow which causes the harmonic or at least an appreciable portion of the same, it can be seen that the voltage rises above zero towards positive values in a rather leisurely way. For this reason the electrons do not bombard the grids very violently and with the power I have had available sol far in my experiments,.I

have not been able to detect any heating effect on the same. It must be kept in mind, however, that it takes considerably more power to make `the grid red than it does to show a change in the temperature on the filament. I have thus reached the conclusion that during the period when the grid is positive it is relatively mildly bombarded by the electrons that settle on the same which means good efficiency due to less heat loss.

When the grid again goes negative, it does so along an increasingly sloping curve. This means that those electrons which did not reach the grid will stop their radial motion towards the same .and before they have moved very far will be subject to a strong voltage gradient in the `opposite direction. This will give them a strong impetus towards the filament so that they reach the same ln a highly accelerated condition. The fact that the electrons are all the time subject to a magnetic field, tends to give to the electrons a still higher absolute velocity. This effect from the magnetic field is rather pronounced and most of the extra heating of the filament disappears if the magnetic eld is removed. In spite of this extra loss, however, the total efficiency of the device is much greater with the field than without. This fast return of the electrons, no doubt, contributes a portion of harmonic energy as an analysis shows that this phenomenon will cooperate in phase with the primary one.

In addition, I have found it rather essential to employ tubes with cylindrical and concentric elements. Moreover, I have discovered that it is necessary that the filament should possess concentric symmetry. The reason for requirements of such symmetry are readily understandable when it is considered that good operation depends upon uniform velocity andl orderly front, so to speak, of the electrons. 'Iypes of filaments which possess and satisfy these qualities are the single wire type, the lspiral and the cylindrical heater type. Until heater type of cathodes are manufactured so that their heating surfaces are less sensitive to back radiation from the grid. making electron emission unstable, other forms of cathodes such as the straight wire type, will be found preferable. It is therefore to be clearly understood that while the cathodes in the various tubes illustrated in connection with the master oscillator and magnetic frequency multiplier modulator tubes and the like, have been illustrated in conventional form, it should be understood that they may be of any one of the types adverted to and also as illustrated in Figure 5, may be of the A. C. energized type.

While it is true that for these very high frequencies, cylindrical two element tubes of concentric symmetry are desirable, as both the fundamental and harmonic frequencies could be placed upon and taken from the same electrodes, I make very good use of three electrode tubes and especially with the third electrode or plate therein.

It should be clear that in a frequency multiplier device the multiplier must be connected to. two tuned circuits, the fundamental input circuitv and the harmonic output circuit'. Accordingly, this forms a problem in all types of frequency multipliers, and the problem is not minimized in my vpresent invention. By connecting the input circuit to the plates and the output circuit tothe grids, and also by tuning the filament circuitfl V` aosas'ra have provided an emcient circuit and one which may very easily be handled.

The detailed circuit is shown, of course, in Figure 1, but, further understanding thereof may more readily be appreciated by referring to Figure 5, a simplified wiring diagram omitting the magnetic iield and showing the instantaneous voltages on the grids and plates of my frequency multiplier.

It should be understood that maximum output at harmonic frequencies is obtained when the space between filament and grid has the maximum voltage gradient swing that a certain power input will allow. This means that the grid especially should have a great voltage swing. In order to obtain such a swing the grid must be tuned to the fundamental frequency by a circuit that has its maximum impedance at the grid. The grid however, must also be tuned to an output circuit of suitable impedance to the harmonics. Such a combination is usually difficult to arrange without the use of heavy circulating current circuits which have high losses. As the distance from the seal of the glass to the grid is considerable in most tubes, this tends to make it increasingly diicult to arrange an external double circuit connected to the grid which would produce thied above mentioned phenomenas right at the gr In order to obtain the high voltage on the grid and at the same time have an easily handled circuit, I utilize the capacity between the plate and grid as an impedance transformer. In this particular case it so happens that I obtain good results when I make the circuit between the grids (in a pushpull device) approach a tuned short circuit for the harmonic. This is, however, not a true short due to loading. Thus, as shown in `Figure 5, it is about a half wave long for the harmonic.

This condition makes this link an inductance to the fundamental frequency. If now surface is indicated in Figure 5 by the dot and dash lines) it can be given such a radius that the capacity between this surface and the grid will have as much capacitive reactance for the fundamental -frequency as the tie between the grids has inductive reactance. The circuit from one of our imaginary surfaces through the grids and the tie to the other imaginary surface is therefore a series tuned circuit. The remaining capacity between our imaginarysurfaces and the plates can now likewise be tuned to the fundamental and its inductive tie between the plates be used also for input coupling. If the aforesaid capacity between the plates and the imaginary surfaces is greater than between the same surfaces and the grids, then the reactance of the former will be lower. Thus when current of the fundamental frequency circulates through the combined circuit, the highest voltage point will be on the grid which at the same time is tied to or faces into a circuit of low impedance for the harmonic.

It may be remembered that it was stated that a two element tube would be the most desirable for my purposes. It should be understood, however, that unless the leads of the anode, in particular. are made very short or the walls of the anode be either close to the glass envelope or form the envelope itself, the above described circuit conditions will ,bev difiicult to m'eet. In case the anode *(the' grid) can be brought close to the external surroundings, then it will be easy to surrv-roun'd'it with va sleeve of correct dimensions which Y will allow most emcient voltage transformation and also allow the fundamental and harmonic circuits to blend in a happy manner. The tuning of the lament circuit has very much to do with this blending, in fact it is a sort of convenient magic wand with which I compromise the tuning conditions for both fundamental and harmonic frequencies in order to reach optimum efhciency.

Reverting back to Figure 5 for the moment, while the input is shown inductively coupled to the plates, and comprising conductors only approximately one-quarter wave length long, it should be understood, as will be evident to those skilled in the art, that the couplings illustrated in Figure 5 and in Figure 1, are, in view of what has been said, equivalent. Voltage nodal points |63, |65, may be tied together by short circuiting conductor |67 which may be in the form of an I incandescent lamp, which, in the absence of light oscillator tubes, odd harmonics are available from a given fundamental frequency applied to the frequency multiplier. However, if it is desired to obtain even harmonics this can be accomplished'- by a push-pull-push-push arrangement or by single tube circuits. Also odd harmonics can, of course, be obtained with single tube circuits. Such variations in my arrangement are easily understood by those familiar with the art.

Odd harmonics are fed into the absorption circuit or modulation link circuit A. S. as already Iexplained, and eventually transmitted by means of transmitting antenna T. A.

For telegraphic signalling, at some point intermediate the antenna and the output circuit of the frequency multiplier, known forms of keying apparatus may be inserted, or known types of chopper wheels for that purpose.

For complex wave modulation however, such as voice modulation, or multiplex signalling, it will be found that the ordinary or conventional schemes of modulation as already pointed out, fail because of inordinate frequency variation in the final output.

Accordingly, another very important feature of my present invention is my improved modulating system comprising, as illustrated, the absorption circuit or system A. S. and the magnetic modulator M. M.

The harmonic frequency output is taken from points of relatively high impedance in the output circuit comprising loop 9B through blocking eondensers |92, |96 and fed to points of a* similar high-impedance in the absorption circuit A. S. The absorption circuit A. S. comprises aconductive loop |86 slidable within conductors |98, 200. This absorption circuit is tuned by adjustment of the loop |96 within the conductors |98, 200 to the harmonic frequency.

Because of the tuned and closed condition of the absorption circuit, it is obvious that standing waves are set up thereon. To points of high and preferably maximum potential, 202, 20d. in the absorption circuit, I couple through conductors 206, 2% vthe tunable control grid circuit 2|@ of electron discharge devices 2|2, 2| i forming part of my improved modulation system.

As illustrated, the tuned circuit 2m consists of conductors 2|6, 2|8 within which and conductively in contact-therewith is slidable loop 220 for tuning purposes. The conductors 2|, Zit are connected respectively to the control grids 222 and 224 of electron discharge devices' applying a unidirectional magnetic field to the modulator tubes 2|2, 2|4, being identical with that given for the frequency modulator, and the magnetic apparatus 228, for the magnetic modulator, also will not be again described.

It is to be noted in connection with the magnetic modulator, that the anodes 230, 232 are floating, that is, left disconnected. However. if desired. a tuned circuit similar to any of the anode circuits described hereinabove, may be connected thereto. Now, it will be found that if it is attempted to modulate, with conventional schemes, the energy in the absorption circuit, for example, by by-passing that circuit to ground through a variable impedance in the form of electron discharge devices, variations in the .iirect current through the impedance device in accordance with modulating potentials will produce-only innitesimal effects upon the energy in the absorption circuit. This is due to the fact that the capacitance of the device prevents any appreciable electron moving voltage to build up at these very high frequencies. Only by careful lining up of the electrons will it be possible to make them respond to these small voltage varia tions. Moreover, the low electron velocity within the ordinary tubes also militates against their use as modulators.

However, with my improved tube absorbing circuit comprising tubes 2|2, 2M, modulation is readily accomplished as the characteristics of the tubes are greatly changed, with the application of the magnetic field thereto.

In other words, by causing the electrons to be suspended in orbits near the grid, due to the effect 'of' the magnetic'iield. a greater number of electrons are available to be eiccted by medirlating potentials.

The grids are in this case preferably having a positive bias so that they at all times are posi tive. In this way, electrons of tangential motion versus the grid are at all times available in great numbers in the extreme vicinity of the grid so that even though low, potentials of high irequency can spend work on the same with the result that absorption takes place. To vary the potential level upon the control grids of the magnetic modulator, thereby varying the absorption of energy by making a greater or smaller number of electrons available and thereby accomplishing modulation of the waves in the absorption circuit. incoming modulation from a source (not shown) is applied through a transformer 234 to a plurality of electron discharge device ampliers 236 connected in parallel. These audio frequency ampliiiers may have their filaments energized by a source of alternating currents (not shown) through a transformer 238. Anode potential is supplied through conductor 240 from a source (not shown) in which there is serially connected a choke coil 242 for audio frequency currents. This choke insures the ow o1 the varying amplified modulating currents through a potentiometer or resistor 246.V

The xed or normal bias on the control grids of the modulator tubes is derived from resistor 244 through variable'tap 246 and conductor 246. A choke 250 is placed in series with a conductor 248 for a purpose which will be explained more fully hereinafter.

As the tapping point 246 giving a correct D. C. bias level for the grid electrodes of the magnetic modulator tubes may-be erroneously placed as regards desired audio voltages which itis desired to apply to the control grids, the choke 250 as already indicated, has been placed in series with conductor 248. f This choke prevents the flow o f substantially all audio frequency currents or potentials from point 246.

However, to apply the high audio frequency potentials arising at point 252 to the modulator control grids, I connect conductor 248 to that point through an audio frequency by-passing condenser 254, which of course is relatively `large as compared to a radio frequency by-pass condenser. Thus, by means of this condenser-choke coil arrangement tapped on to resistor 244, I am enabled to apply at the same time to the control grids of the magnetic modulator, the desired high audio frequency voltage and the relatively low value uni-directional polarizing potential.

As already pointed out, the variations in potential on the control grids of the magnetic modulator tubes vary the amount of energy absorbed from the absorption circuit, as a result of which through,ad justable coupling C-2 and transmission line 256 there is fed to the transmitting antenna T. A. an amplitude modulated wave of substantially constant frequency.

The transmission line construction T. L. follows the construction given in my United States Patent No. 2,000,032, granted May "I, 1935. Briey the harmonic modulated carrier energy travels through transmission line 256 through building wall 258 over transmission lines 260, 262 and 264 to the feeder Wires 214 for radiating or transmitting antenna T. A., which is provided with a smooth plane metallic reflector 212.

The transmitting antenna comprises a plurality of linear radiators 216 each substantially onehalf wave .length long arranged coaxially with each other and parallel to another group of half wave radiators 218. The radiators 21B are also coaxial with respect to each other and parallel to the radiators 216. As indicated, the radiators 216, 218 are formed by bending single conductors 280, 282. These conductors are so bent that alternate half Wave portions thereof form radiating portions as indicated, the cross portions at 282, 28d being substantially parallel and closeA together produce substantially cancelling radiations. Hence, by analysis it will be found that the instantaneous currents in theradiating portions 216, 218 are in like phase as a result of which a bi-directional radiant characteristic is obtained. This bidirectional characteristic is reduced to a uni-directional characteristic by placing a metallic reflector 212 behind the plane formed by the radiating conductors 216, 218 which are arranged in the same linear piane. The spacing between the antenna system and the smooth metallic reecting sheet 212 is preferably made substantially one-quarter wave lengthalthough any substantially odd quarter wave length spacing will produce the desired result. By means of insulators, the radiators may be supported upon the reflector, the insulators being fixed to voltage nodal points on the conductors, for example, the mid-points of radiators 216, 218 and the cross over points of the conductors 280, 282.

To concentrate the beam, several radiating sys- 'audacia `an inspection of the drawings.

.214 is formed of a pair of conductors as illustems may be placed one above the other as illustrated. Energization is accomplished through the common feed line 214 as is apparent from This feed line ilector andantenna may be tilted at any angle so as to project, say, a beam of waves upon a smooth plane' reflector situated, say, on the top of a high tower. The reflector mounted on the tower will in turn reflect the waves at an angle of reection equal to the angle of incidence thereon. For example, a transmitting antenna T. A. may be pointed to a reflector on top of a tower some 500 feet high. The reector may be so positioned that the beam is propagated horizontally until, due to the curvature of the earth, it ap-- proaches the surface of the earth. At this point .another reflector may be provided to say, turn the direction of the beam at right angles to the direction up to that point, to a suitable receiver located at some distant point. Preferably, however, due to unavoidable losses rduring reflection, I prefer to place the transmitting antenna as high as possible and point it directly at a receiving station which may or may not be located in a similar tower. One may also build up systems of curved reflectors with common foci or wire'systems with refractive properties, etc.

For relaying signals, any form of bi-direction antenna may be used. For example, if an antenna hastwo main characteristic ears", one can be A used for the incoming signal and the other tok relay it in another direction. Even unidirectionalv antennae may be used provided the incoming and relayed signals are on the same side of the antenna system.

A modified form of my invention for transmitting waves of the order in frequency of 450,000 kilocycles per second, is illustrated in Figure 2.

In Figure 2, .a primary master oscillating or guiding oscillator 300 is provided. This oscillatoruis ofthe constant frequency type, for exlong line frequency controlled type. The output of the guiding oscillator G. O. is fed to a frequency multiplier and/or amplifier F. M. in whose output circuit 302 there appears the desired fundamental frequency energy. By means of the inductive coupling L. C., the energy of fundamental frequency from output circuit 302 is fed to the tuned cathode energizing circuit 304 of the local master oscillator L. M. O. Preferabiy, this osciuator L. M. o. is so adjusted that it just fails to oscillate without the application of energy from a frequency multiplier and amplifier F. M. or 306. However, upon the application of the energy from the frequency multiplier, the local master oscillator L. M. O. goes into oscillation at a relatively high output and it is frequency guided and controlled or locked into step with the constant frequency oscillations from the frequency multiplier and amplifier 306.

Another way of controlling the frequency of the oscillations ofthe oscillator L. M. O. would be to allow it to oscillate at nearly the fundamental frequency and then `couple the relatively constant frequency oscillations from source 306 thereto. The oscillations generated by the oscillator L. M. O. will be-locked or guided into step with the oscillations supplied by the harmonics of the guiding oscillator, but, of course, the control will be to a lesser degree than in the case previously referred to wherein the master oscillator L. M. O. is adjusted to be on the verge of oscillating rather than actually independently oscillating.

The frequency controlled output of the local master oscillator L. M. O. is fed to a magnetic frequency multiplier M. F. M. similar to the one described in connection with Figure 1. The output of the magnetic frequency multiplier in turn is fed to an absorption circuit A. S. to which at suitable voltage maximum points I couple my improved magnetic modulator M. M. to modulate the carrier energy transmitted by the transmitting antenna T. A., in accordance with the output of the vaudio amplier A. A.

To go into greater detail concerning the structural features of the arrangement shown in Figure 2, the electron discharge device oscillators or high vacuum tubes 308, 31,0 are provided with a tunable anode circuit 3I2, a tunable controlV ving circuit 304. The tuning means, as in connection with Figure 1, may take the form of tromboneslides within the various circuits, or may be short circuiting straps to which D. C. connections are made, but, for the sake of simplicity they have been omitted. The cathode energizing conductors 3I6,` 3I8 may be, as illustrated, simple linear conductors adjustable in length and arranged so that the portions leading to each filament are relatively close together as to prevent radiation therefrom. Or. the tubular system shown in Figure 1 may be utilized. The conductors 3l6, 3I0 are short clrcuited for high frequency currents at their ilament ends by bypassing condensers 320, 322 so that lwith respect to radio frequency currents, the portions of the conductors 3|6, 3I8 leading to each lament act in parallel, it being remembered, however, that the pairs of conductors, namely, considering the pair leading to the filament to tube 308 and the pair leading to tube 3|0, act in series for the high frequency currents.

Preferably, the coupling L. C. is tapped on to the filament tuned circuit at points 3I1, 319 of such impedance that there will be a minimum of reaction upon the guiding oscillator with a change in load upon the local `master oscillator L. M. O.

If desired, however, the coupling may be made at a high or low voltage point or high impedance point on the cathode energizing circuit. The grid tuning circuit 314 is grounded at a voltage nodal point through resistor 324, which, through grid rectication, furnishes suitable D. C. control bias upon the grids.

'I'he anodes of the tube L. M. C.' are supplied with direct current potential through a voltage regulator V. R. which maintains constant voltage upon the anodes of tubes 308, 310 despite fluctuations in the output of the rectier 326.

The action of the voltage regulator V. R. is similar to that given to the voltage regulator in Figure 1. variations in voltage across resistance 320 causing variations in current ow through' vacuum' tube 330, as a result of which varying voltage drops across resistor 334 occur in such a magnitude as to compensate vfor voltage variations in the output circuit of rectifier 326, thereby maintaining constant voltagein conductor 332 and lhence upon the anodes of the oscillator tubes 308. 3| 0.

Filament heating or energizing energy for both the magnetic frequency multiplier M. F. M. and the local master oscillator L. M. O., is supplied from source 334 which, though illustrated as a battery, may obviously be any form of uni-directional current. Uni-directional current, of course, for this purpose is preferred although A. C. types of filaments may be utilized. One end of the lilament energizing source is grounded at 336, and, through the conductors388 feed the tuned cathode circuit of the local master oscillator L. M. O. through voltage nodal points on the tuned circuit 304, the ilxation of this point may be further secured as is desirable, by the action of by-passing condenser 340, and 342.

By inductively coupling the tunable anode circuit 344 of the magnetic frequency multiplier M. F. M. to the anode circuit of the local master oscillator, fundamental frequency energy is applied to the anodes of the magnetic frequency multiplier M. F. M. The anode circuit of the magnetic frequency multiplier tubes 346, 348 is accomplished by variation of Vadjustable slides 350. 'I'he heating circuit 352 of the magnetic frequency multiplier M. F. M. is tuned for best matching for the rest of the circuit. This tuning may or may not be either'the fundamental or harmonic frequency which it is desired to produce.

I'he magnetic field, longitudinally applied to the tubes 346, 348 in the arrangement shown in Figure 2 is accomplished by the action of solenoids 354, 356 which may be Wrapped about or simply placed about the tubes 346, 348. Moreover, if desired, the solenoids may be provided with magnetic cores or the magnetic arrangement may take the form described in connection with Figure 1. 'I'he intensity of the magnetic ield is, of course, controlled by the variation of either or both of Asource 360 and resistor 362.

The arrangement shown in Figure 2 has been simplied as illustrated to the extent that the buffer amplifier of Figure 1 has been omitted. The coupling from circuit A. S. to the absorber or modulator tubes 406 and 408 is shown in a simplied way. Through the action of resistor 366 suitable grid bias is maintained upon the grids of the tubes 346, 348, the resistor being connected to a short circuiting conductor 368 variable along the conductors 310, 312 forming part of the circuit A. S. as well as the tuned grid circuit. The grid circuit as in Figure 1, forms the output circuit of the magnetic frequency multiplier, the short circuiting strap 368 being connected as indicated across voltage nodal points on the circuit A. S. whereas the conductors 314, 316 .connected to the circuit A. S. through by-passing condensers 318, 380 are connected to this circuit at voltage maximum points 31|, 313 thereon, or in other words, at high impedance points.

Modulated harmonic frequency energy is taken from the circuit A. S. through transmission line T. L. inductively coupled thereto which, in turn, is also coupled to transmitting antenna T. A. formed of conductors 384, 386. This antenna is described more fully in my United States Patent No. 1,927,522, supra.

Briefly, due to the nature of wires which are long relative to wave length and due to the relative location of these wires and their relative phase, it will be found that energy is propagated predominantly along the bisector or the angle formed by the conductors 3 84, 386. The attenuation in the conductors at theghigh frequencies involved'is so great for wires 100 waves long, that there is substantially no reflection, as a result of which no reiiector formed of a similar pair of conductors, is required.

The antenna line T. L. may be coupled as illustratedin Figure 3 to pairs of conductors similar to 384, 386, each pair, of course, being arranged in a dierent plane. In Figure 3. the conductors 386, 386 are in one plane whereas conductors 380, 39o are in another plane. These planes may be the horizontal or vertical planes or any planes intermediate the two. The transmitting antenna T. A. of Figure 2 may, of course, be arranged in either a horizontal plane, a vertical plane or in any plane between the horizontal and vertical, and the antenna system of Figure 3 may be rotated any angle about the bisector of the solid angle formed by the conductors.

Modulation, as already indicated, is accomplished by absorbing variable amounts of energy corresponding to amplitudes of the modulating potentials, from circuit A. S. by means of modulator or absorber tubes 606, 08. In particular, amplified modulating potentials from, for example, microphone 392, are fed to an audio ampli'- fier 394, which, through the action of transformer 396, impresses those potentials through conductor 398 short clrcuiting strap 400 and conductors M2, 606, to the grids of electron discharge devices 406, 408 of my magnetic modulator. To make. doubly sure no fundamental energy gets through and becomes modulatedto give back reaction, short `circuiting conductor $03 is provided.

To maintain proper bias upon a control grid upon magnetic modulator M. M., a uni-directional source of potential dit is provided. As before, the cathode energizing circuit di@ of the magnetic modulator M. M. is tuned. The anodes of electron discharge devices tile, of the netic modulator may be left floating that is, completely disconnected, or short circuited by short circuit 4t2. However, if desired, circuit tit may be tuned to the harmonic or, in other words, to the samefrequency as that to which the absorption circuit A. S. M. M. is tuned.

The solenoids Sid, l i 6 are energized by a source @is and produce a uni-directional magnetic eld which, of course, is applied to the electron now within the modulator tubes MS, tilt. 'i

As I have already pointed out, my improved magnetic modulator is the only arrangement wherein desired variable absorption from the transfer circuit A. S. can take place.

Certain circuit re-arrangements of this modulator arrangement may be made in the manner illustrated in Figure 4. Modulating potentials in the arrangement shown in Figure d are applied to the grid-cathode circuits of the parallel connected modulator tubes @28. Direct current potential for both the modulator tubes t2!) and the magnetic modulator M. M., in the latter of which, by the way, the magnetic apparatus has been omitted for the sake of simplicity, is supplied through conductor 422. The modulator reactor tZd is chosen so as to have practically no D. C. resistance. Consequently, the grids and laments of the modulator tubes @26, t28 will be at the same D. C. potential except for the drop in D. C. potential across resistor 63d. However, since the current drawn through choke 62d is constant through its inherent action, the

aocaevc voltage across 'resistor 432 connected between the anodes and cathodes of the modulator tubes 420, will vary according to the modulating potentials due to the varying current ows therein. Consequently, the voltage upon the grids of the modulator tubes $26, 428 will vary as a result of which varying amounts of current will be drawn from the absorption circuit A. S.

The arrangement shown in 'Figure 4 offers the advantage of eliminating in the modulation circuit blocmng condensers. such as condenser 25e of Figure l. Moreover, this arrangement shown in Figure 4 has the added advantage that, because of resistance coupling, the circuit is extremely stable, is of fine delity, and greatly simplifies operation.

Although I have shown the lament tuning conductors to be the means for conveying heating currents to the ilaments of the various tubes. heating currents'may be supplied through chokes to the filaments, the tuning conductors in that case carrying only high frequency currents and if desired blocked oi from the'heating currents by means of large blocking condensers.

As I have already stated. my Present invention is not limited to pushpull tube arrangements, but may be applied equally as well to single tube arrangements and to arrangements utilizing other forms of modulation than amplitude modulation. In Figure 6 I have illustrated diagrammatically an arrangement wherein single tube stages are utilized and wherein the ensuing output is frequency modulated.

The arrangement shown in Figure 6 utilizes a master oscillator M. 0. supplying an improved single tube magnetic frequency multiplier M. F. M. whose output is frequency modulated and fed to a suitable transmitting antenna T. A.

Cathode heating energy for the cathode of the master oscillator tube .500 is supplied through concentric conductor 502, tubular in form, and internal conductor after being impressed thereon through the medium of transformer 506. The potentiometer die is really not needed if the potentiometer el? is present in the grid circuit. The iilament of tube 500 may be heated by direct current and the arrangement shown in connection with tube S23 may be used wherein the potentiometer 56@ serves the dual purpose of regulating cathode bias and cathode heating current. It is to be clearly understoodthat either arrangement maybe used on either tube.

The slider de contacting with tube 5%2 and slidable along grounding strip 5m, (see Figure 7) in turn fastened to grounding plate SI2 insulatingly separated from the shield or container 5M by means of thezcondenser dielectric strip 5w, is used to tune or adjust the impedance of the cathode high frequency circuit formed by the tube 502 and in effect ground Sie.

A similar sliding arrangement 511e is used to tune the grid circuit comprising linear conductor 521i.

High frequency/'oscillations generated by the master oscillator are fed from the anode 522 through the adjustable tuning trombone 52d, D. C. blocking condenser or radio frequency bypassing condenser 53@ to the input electrode or anode 52s of the magnetic frequency multiplier tube 52a. The anode circuits of the master oscillator be@ and the magnetic frequency multiplier are 'formed similarly to the cathode circuit of the master oscillator and are similarly l similarly to the magnetic frequency. multipliers hereinabove described and is provided with a solenoid 548 in order to apply longitudinally of the tube y528, a uni-directional magnetic eld.

.The output electrode 542 is the normal grid electrode or electrode adjacent the cathode of the tube 528 and is tuned to a harmonic of the input frequency by means of slider 558. 'The cathode circuit of the magnetic frequency multiplier is adjusted in impedance by means of a slider 588 so that the potentials arisingthereon have the most benecial phase relation for harmonic production in the output circuit including conductors 558 and capacitively grounded strip-554. The output conductor 510 is tapped to a point 512 in the output circuit for mostefcient energy transfer to the radiating linear antenna 518 as illustrated. the transmission line 518 containing an adjustable trombone slide B16. For more perfect balancing, this coupling may be inductive rather than conductive.

In the arrangement illustrated in Figure 6 (and this is true of any of the arrangements heretofore described) frequency modulated energy may be obtained by simply varying the voltage on any of thecold electrodes of the magnetic frequency multiplier and/or master oscillator. 'I'he frequency variation thus obtained is at these very high frequencies very much greater in magnitude than the inherently obtained amplitude modulation. For this purpose, in connection with Figure 6, the voltage on the cold electrode 542 of the magnetic frequency multiplier, is wobbled by means of transformer 518 supplied with alternating currents from a suitable source 580 and keyed by means' of a keyer 582. This alternating voltage from source 581i is superimposed upon.

the unidirectional voltage impressed upon cold electrode 542.

Similar results could be'obtained by inserting the transformer 518 in the anode lead of tube 528, or in the anode or control electrode leads of the master oscillator tube 580, or, in connection with the pushpull arrangements, any similar polarizing leads. It is also to be clearly understood that the source of alternating currents 580 and the keyer 582 may be replaced by a microphone or similar source of alternatingcurrents. The alternating modulating potentials may also be applied in series with the source of energy energizing the solenoid 540 for modulating purposes.

In the event that it is desired to radiate from linear radiator 51d an amplitude modulated wave, an absorption system employing the principles hereinbefore delineated is preferably utilized.

Should it be desired to use a pushpull absorption scheme, the output circuit may be arranged as shown in Figure 8.

Then, the output trombone 516, is connected to output inductor loop 58u grounded by means of conductor 582. The antenna 514 is coupled to the loop 580 by adjustable loop 582 and adjustable transmission line 584. For amplitude modulation purposes, energy may be drawn from line 585 as illustrated by the tube arrangement heretofore described. 4

My frequency multiplication action may be carried into effect by the use of a tube having a cylindrical split anode, and a linear lament ar` ranged coaxially with the split anode, the split anode being in the form of two troughs completely insulated from each other arranged on either side of the linear filament. Fundamental input potentials may be applied to the two halves of the anodes through a simple linear conductor tunable circuit such as described, and, at suitable points along the conductors, a suitable harmonically tuned circuit may be connected or coupled thereto. Application of the magnetic field in a direction coaxial with the linear dimension of the lament will, of course, give the harmonic output in the harmonically related circuit. Preferably, in such an arrangement, two,- linear tuned circuits should be used. Each of the open ends of one of the circuits should be connected to different ones of the anode sections as should also be connected the open ends of the conductors of the other circuit. One of these circuits may then be adjusted to apply fundamental frequency energy to the anode sections and the other circuit may be adjusted to have harmonic waves set 'up therein. In other words, such a system will replace the pushpull arrangement of tubes and make use of a common linear filament or cathode, the heating leads for which may be drawn out through the slits between the anode sections and through the side of the tube at'a position intermediate the length of the anode.

Such a frequency multiplying system for use in connection with a phase modulation transmitter is illustrated in Figure 9. Oscillations from a crystal controlled oscillator 608 are amplified by means of a. buffer amplifier 602 in turn supplying energy to the phase modulator tubes 684, 68E, through the inductive reactance 608 and capacitive reactance 6H) respectively. Signal energy is applied to the screen grids of the tubes 684, 60B in phase opposition through the intermediary of transformer 608 as a result of which, the tubes 604, 606 become alternately more conductive. In this manner, there appears in the common output circuit 6i! constant frequency energy but shifted in phase in accordance with the signal or audio frequency input applied l to the screen grids of the tubes 604, 606.

The output of circuit SI2 is fed to succeeding ampliers and frequency multipliers 6M, the frequency multiplication action of which serves to augment the phase shift caused by the modulation. When the output of the frequency multiplier and amplifier 6M is of desired value, it is applied to the tuned fundamental frequency input circuit GIS of the magnetic frequency multiplier 6| 8. Tuning of the fundamental frequency circuit BIG is accomplished as before by preferably the use of adjustable trombone' slide 628. The conductors ofthe circuit 816 are connected to the split anodes 622, 824 insulated from each otherand arranged concentrically about a coaxial linear filament or cathode 626 supplied with energy from a heating source 628. The cathode 626 may be grounded, or, insulated from ground for extremely high frequencies by means of radio frequency chokes inserted in the heating leads from source 628. Magnetic field applied by the field coil of the magnetic frequency multiplier is applied coaxial with the linear filament 628 and causes action heretofore described.

The eld coil produces a magnetic field in accordance with the current from source 630 regulated by potentiometer 632. 'I'he output circuit 835 of the magnetic frequency multiplier is tuned to a harmonic frequency and also is connected as illustrated to the split anodes. Frequency multiplied energy may then be taken inductively from the output circuit 634 to the adjustable transmission line 636 and fed to a suitable radiating antenna not shown.

The split anodes may be made of carbon or any 

